Klystron with added inductance in resonant cavity



A ril 28, 1970 w. SCHMIDT KLYSTRON WITH ADDED INDUCTANCE IN RESONANT CAVITY Filed Nov. 8, 1967 FIG.2

INVENTOR. WOLFGANG SCHMIDT AGENT United States Patent Office 3,509,413 Patented Apr. 28, 1970 Int. Cl. rioi 23/20 U.S. Cl. 3155.52 5 Claims ABSTRACT OF THE DISCLOSURE A high-power klystron is provided with a resonant cavity into which extend two tubular electrodes, the ends of which are spaced apart forming a gap therebetween. A cylindrical member is positioned around at least one of the tubular electrodes without a gap between either the electrode or wall of the cavity and the member. This member operates as an inductance permitting the cavity to be tuned.

The invention relates to a klystron, particularly a highpower klystron for use in television transmitters, said klystron comprising inter alia a gap electrode and a drift electrode arranged axially thereto, each electrode terminating in an evacuated klystron chamber, whilst at least one of the electrodes extends in the interior of the evacuated klystron chamber and a so-called high-frequency gap is formed between the electrode ends terminating in the evacuated klystron chamber or penetrating into the interior thereof.

It is known that a klystron comprises at least two klystron chambers, on each side of which, for example, via electrodes, an electron gun and a collecting electrode respectively are connected. The klystron chamber itself may be formed by an evacuated hollow space into which extend the electrodes, for example, the drift electrodes or gap electrodes.

These electrodes are axially orientated and arranged so that in the klystron chamber between the electrodes a greater or smaller gap is formed, which may be termed high-frequency gap or interaction space. The evacuated klystron chamber is surrounded by non-evacuated klystron chambers in which also means for tuning the chambers may be accommodated.

The tuning range and the quality of such a klystron chamber consisting inter alia of the evacuated klystron chamber and the non-vacuated klystron chamber, depend upon the effective gap capacity loading the klystron chamber. If this load is small, the klystron chamber has a high quality and a large tuning range. When the high-frequency gap is enlarged by increasing the distance between the driftor gap electrodes in the evacuated klystron chamber the eflective gap capacity is reduced and hence also the load of the klystron chamber. An increase in distance between the electrodes, however, brings about incrased coupling looses and hence a considerable decrease in energy amplification and of the useful effect of the klystron.

The invention has for its object to reduce the load of the klystron chamber by reducing the eflective gap capacity and to reduce in this way the efiective gap capacity itself without an increase in distance between the electrodes in the evacuated klystron space.

In contrast to what is described in U.S. patent speci fications 2,480,462 and 2,815,467 with respect to the frequency variation of a magnetron oscillator and of a reflex klystron respectively this is not achieved by providing in the chamber means for varying the volume of the resonant cavity, since by this known measure, it is true, the frequency can be adjusted, but the quality and the tuning range of the klystron chamber cannot be increased without a simultaneous change of the coupling in the high-frequency gap or interaction space.

The invention provides the possibility of attaining the purpose aimed at by carrying out measures involving only a slight variation of the volume of the evacuated klystron chamber. The klystron according to the invention which has a larger tuning range and a higher quality with the same electrode distances in the evacuated klystron chamber, is characterized in that at least one of the electrodes is surrounded by a prolongation electrode which operates as an inductance.

The prolongation electrode and the electrodes surrounded thereby may be made from the same piece of material. It may alternatively be secured on one side to a flange of the klystron. The prolongation electrode may have the shape of one or more pole pieces projecting across the flange of the klystron. They are made of soft iron that is to say of a material diiferenting from that of the drift and gap electrode and serve to define a direction of the magnetic field in the klystron chamber.

In one embodiment of the invention to prolongation electrode may have a greater dimension in an axial direction than in a radial direction.

The invention will be described more fully with reference to the drawing in which FIGS. 1 and 3 show one embodiment wherein the prolongation electrode projects across the flange of the klystron and FIG. 2 shows another embodiment in which the prolongation electrode is a pole-piece.

The figures show a gap electrode 1 and a drift electrode 2, projecting through a klystron flange 3 and 4 respectively and being orientated axially. The klystron flanges 3 and 4 are secured to each other, for example, by a ceramic tube 5, so as to be electrically insulated from each other. The evacuated klystron chamber is designated by 6. Into this chamber project the end 7 of the gap electrode 1 and the end 8 of the drift electrode 2, so that a high-frequency gap 9 is formed between said two ends. According as the distance between the ends 7 and 8 is larger, the high-frequency gap and hence the tuning range of the klystron are greater, but the useful effect and the energy amplification of the klystron are then lower.

According to the invention each of the gap electrodes 1 may be surrounded by a prolongation electrode 10. When the gap and drift electrodes 1 and 2 have an annular shape, the prolongation electrode may also be annular in shape and, as is shown in the FIGURES 1 and 3, it may be secured to the electrodes 1 and 2 and the klystron flanges 3 and 4.

According to the invention the provision of at least. one prolongation electrode 10 with a given high-frequency gap 9 considerably enlarges the tuning range oi. the klystron chamber, since the increase in inductance of the gap electrode brought about by the prolongation electrode 10 is equivalent to an electric prolongation of the gap electrode so that the effective gap capacity loading the klystron chamber is reduced. In the substitute diagram the klystron chamber as a whole, that is to say the evacuated klystron chamber and the klystron chamber(s) non-evacuated and joining the former, is loaded by the gap capacity, which is in series with the inductance of the gap electrodes, in this case the inductance of the gap electrode 1 and the drift electrode 2.

The prolongation electrodes may also form the ends of pole pieces 11 (FIG. 2) of a magnetic system, which ends project in the evacuated klystron chamber for orientating the magnetic field in the evacuated klystron chamber in the desired manner.

What is claimed is:

1. In a klystron, a pair of spaced aligned tubes extending into an evacuated chamber forming a resonant cavity, and a cylindrical inductive member surrounding one of said tubular electrodes without an intervening space therebetween, said cylindrical member having one surface which abuts the wall of said chamber through which said electrode extends.

2. A klystron as claimed in claim 1 in which the cylindrical electrode is constituted of the same material as the electrode which it surrounds.

3. A klystron as claimed in claim 1 in which the cylindrical member is secured to the wall of the chamber which it abuts.

-4. A klystron as claimed in claim 1 in which the cylindrical member is a pole-piece which extends through the wall of said chamber.

5. A klystron as claimed in claim 1 in which the cylindrical member has a large axial dimension than radial dimension.

References Cited UNITED STATES PATENTS 2,413,364 12/1946 McCarthy 3155.52 2,621,304 12/1952 Altovsky 3155.52 X 2,929,955 3/1960 James 3155.52 X 3,250,947 5/1966 Fiedor 315-552 X 3,390,301 6/1968 Sawada et a1. 315-552 X HERMAN KARL SAALBACH, Primary Examiner SAXFIELD CHATMON, JR., Assistant Examiner US. Cl. X.R. 315-5.5l; 333-83 

